Observable signature of a background deviating from the Kerr metric

Journal Article · Tue Jun 15 00:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.81.124005· OSTI ID:21413220

Lukes-Gerakopoulos, Georgios ^[1]; Apostolatos, Theocharis A ^[2]; Contopoulos, George ^[1]

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1. Academy of Athens, Research Center for Astronomy, Soranou Efesiou 4, GR-11527, Athens (Greece)
2. Section of Astrophysics, Astronomy, and Mechanics, Department of Physics, University of Athens, Panepistimiopolis Zografos GR15783, Athens (Greece)

By detecting gravitational wave signals from extreme mass ratio inspiraling sources (EMRIs) we will be given the opportunity to check our theoretical expectations regarding the nature of supermassive bodies that inhabit the central regions of galaxies. We have explored some qualitatively new features that a perturbed Kerr metric induces in its geodesic orbits. Since a generic perturbed Kerr metric does not possess all the special symmetries of a Kerr metric, the geodesic equations in the former case are described by a slightly nonintegrable Hamiltonian system. According to the Poincare-Birkhoff theorem, this causes the appearance of the so-called Birkhoff chains of islands on the corresponding surfaces of section in between the anticipated KAM curves of the integrable Kerr case, whenever the intrinsic frequencies of the system are at resonance. The chains of islands are characterized by finite width, i.e. there is a finite range of initial conditions that correspond to a particular resonance and consequently to a constant rational ratio of intrinsic frequencies. Thus while the EMRI changes adiabatically by radiating energy and angular momentum, by monitoring the frequencies of a signal we can look for a transient pattern, in the form of a plateau, in the evolution of their ratio. We have shown that such a plateau is anticipated to be apparent in a quite large fraction of possible orbital characteristics if the central gravitating source is not a Kerr black hole. Moreover, the plateau in the ratio of frequencies is expected to be more prominent at specific rational values that correspond to the strongest resonances. This gives a possible observational detection of such non-Kerr exotic objects.

• OSTI ID: 21413220
• Journal Information: Physical Review. D, Particles Fields, Vol. 81, Issue 12; Other Information: DOI: 10.1103/PhysRevD.81.124005; (c) 2010 The American Physical Society; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANGULAR MOMENTUM
BLACK HOLES
CHAINS
DETECTION
EQUATIONS
EVOLUTION
GALAXIES
GRAVITATIONAL WAVE DETECTORS
GRAVITATIONAL WAVES
HAMILTONIANS
INTEGRAL CALCULUS
KERR METRIC
MASS
ORBITS
RESONANCE
SIMULATION
SURFACES
SYMMETRY
MATHEMATICAL OPERATORS
MATHEMATICS
MEASURING INSTRUMENTS
METRICS
QUANTUM OPERATORS
RADIATION DETECTORS